CVE-2009-2979 in Acrobat Reader
Summary
by MITRE
Adobe Reader and Acrobat 9.x before 9.2, 8.x before 8.1.7, and possibly 7.x through 7.1.4 do not properly perform XMP-XML entity expansion, which allows remote attackers to cause a denial of service via a crafted document.
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Analysis
by VulDB Data Team • 08/24/2021
Adobe Reader and Acrobat versions prior to 9.2, 8.1.7, and potentially 7.1.4 contain a critical vulnerability in their XMP-XML entity expansion handling mechanism that enables remote attackers to execute denial of service attacks. This vulnerability stems from insufficient validation and processing of XML entities within the Extensible Metadata Platform implementation, which is commonly used for embedding metadata within PDF documents. The flaw occurs when the software encounters maliciously crafted XML entities that trigger excessive resource consumption during parsing operations, ultimately leading to application instability and potential system crashes.
The technical nature of this vulnerability aligns with CWE-776, which specifically addresses improper restriction of XML external entity expansion. When Adobe Reader or Acrobat processes a PDF document containing crafted XMP metadata, the XML parser fails to properly limit the expansion of entities, allowing attackers to construct documents that cause the application to consume excessive memory and processing cycles. This creates a condition where the application becomes unresponsive or terminates unexpectedly, effectively rendering the software unusable for legitimate users while maintaining the attacker's ability to repeatedly exploit the flaw.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on Adobe Reader for document processing and viewing. Attackers can craft malicious PDF documents that appear legitimate to end users, potentially leading to widespread service disruption across enterprise environments. The exploit requires no special privileges or authentication, making it particularly dangerous as it can be delivered through email attachments, web downloads, or file sharing platforms. The denial of service impact extends beyond individual user experiences to potentially affect entire document processing workflows and business operations.
Organizations should prioritize immediate patching of affected Adobe Reader and Acrobat installations to mitigate this vulnerability. The recommended mitigation strategy involves updating to Adobe Reader 9.2 or later, 8.1.7 or later, or 7.1.4 or later versions where available. Additionally, implementing network-based controls such as PDF content filtering and sandboxing mechanisms can provide defense-in-depth protection. Security teams should also consider deploying endpoint protection solutions that can detect and block suspicious document processing activities, while maintaining regular vulnerability assessments to identify potential similar flaws in other document processing software. The ATT&CK framework categorizes this vulnerability under T1499, which covers network denial of service attacks, highlighting the importance of maintaining robust network security controls and incident response procedures for such threats.